The present invention relates to a telephone communication apparatus, and particularly to a fixed subscriber unit for use in a wireless local loop type telephone system.
Recently, a communication method called wireless local loop (hereinafter referred to as WLL) in which a telephone can be used in a general home or business office by wireless, instead of metal wire, in a place where no wire telephone line network is laid has been widely noticed. In the WLL, a wireless base station is set in (or near) a telephone central office so that the wireless base station is connected to the telephone central office by a wire (or wireless) line. Further, a fixed subscriber unit (hereinafter referred to as FSU) is set in a general home or in a business office so that a telephone can be connected to the FSU. The wireless base station and the FSU can be communicated with each other by wireless so that a telephone can be used in a general home or in a business office.
FIG. 9 shows an example of the overall configuration of the WLL. Here is shown an example of the configuration of a WLL system in a general home. In FIG. 9, the reference character A designates a house of a general home; B, an FSU set in the general home; C, a telephone connected to the FSU through a telephone cord; and D, an FSU antenna generally set outside the house. Further, the reference character E designates a wireless base station which performs communication with the FSU by wireless. In the example of FIG. 9, the wireless base station is set outside a telephone central office. The reference character F designates an antenna of the wireless base station; and G, a pillar on which the wireless base station E and the antenna F are set. The wireless base station E is connected to an office equipment I in a telephone central office H through a wire cable. The reference character J designates the whole of a higher-rank network of the telephone central office as a whole.
FIG. 10 shows the internal configuration of the FSU. In FIG. 10, the reference numeral 1001 designates an antenna connector. Because an antenna of the FSU is generally set outdoors, the antenna connector 1001 serves a connector for connecting a cable of the antenna. The reference numeral 1002 designates a wireless circuit. The wireless circuit 1002 performs transmission/reception of wireless data while the frequency and the transmission timing are designated by a wireless control portion 1003. The reference numeral 1002a designates a synthesizer built in the wireless circuit 1002. The synthesizer 1002a generates a signal of the frequency designated by the wireless control portion 1003. The wireless control portion 1003 measures the level of reception on the basis of the wireless data received from the base station and then writes reception level data in a temporary storage memory in a control portion 1005. The reference numeral 1004 designates a channel codec portion for coupling/decoupling data transmitted/received through a wireless control channel and a communication channel. A data in a communication channel is composed of information such as voice data, or the like, and control information to be processed by the control portion 1005. The user data such as voice data, or the like, is signal-processed by voice codec in a telephone line interface portion 1007 without any interposition of the control portion 1005. The reference numeral 1006 designates a memory for storing information necessary for grasping an operating base station, or the like. A nonvolatile memory is often used as the memory. The reference numeral 1007 designates a telephone line interface portion which includes a voice codec portion 1007a, a telephone line circuit 1007b, a reception signal generating circuit 1007c, a telephone off-hook/on-hook detecting circuit 1007d, a telephone dial detecting circuit 1007e, and a tone generating circuit 1007f for outputting a dial tone, a busy tone, a howler tone, or the like, to a telephone. The reference numeral 1008 designates a telephone cord connector for connecting a telephone cord of the telephone connected to the FSU; 1009, an electric source circuit; and 1010, an electric source cord of a direct connection type or a separation type.
The manner how to make transmission, reception and speech by using a general home telephone in the WLL system will be described briefly below with reference to FIGS. 9 and 10 by way of example in the case where the WLL employing a TDMA/TDD (time division multiple access/time division duplexing) personal handy phone (PHS).
In FIG. 9, when the wireless base station E is on standby for communication, in the same manner as a general PHS public base station, the wireless base station E transmits information signals called LCCH (logical control channel) at regular periods to a counter station (CS), that is, to a portable station (PS) in the case of a general PHS system, while to the FSU in the case of a WLL system.
In FIG. 10, after the FSU is powered on, that is, after a power plug of the electric power cord 1010 is inserted into plug socket so that the electric source circuit 1009 supplies an electric source to respective parts, the FSU receives the LCCH of a wireless base station identified by the wireless base station information registered in the memory 1006 of the FSU. Here, the wireless base station information registered in the FSU contains the carrier (frequency) number (commonly called control carrier number) of the LCCH transmitted by the wireless base station, and the system identification code (commonly called system ID) of the wireless base station. That is, after the FSU is powered on, the FSU makes the control portion 1005 control the wireless control portion 1003 to set a frequency in the synthesizer 1002a so as to correspond to the control carrier number on the basis of the information registered in the memory 1006 in the FSU, and further makes the control portion 1005 control the wireless circuit 1002, through the channel codec portion 1004, so as to be in a continuous reception state in order to search for the LCCH of a wireless base station coincident with the system ID registered in the memory 1006.
FIG. 11 shows the burst configuration of the LCCH used in a control carrier of a PHS defined in RCR STD-28 which is a standard specification of the PHS. In FIG. 11, the reference character PR designates a preamble portion, and the reference character UW designates a unique word for synchronization. The unique word UW is followed by base station ID (42 bits) of a wireless base station which is a counter station of the FSU. The data of upper 9 bits in the 42 bits of the base station ID corresponds to the system ID. The base station ID is followed by control information and CRC information.
FIG. 12 is a schematic diagram of a position registration sequence defined in RCR STD-28. If the upper 9-bit data (namely, the system ID) of the base station ID in the LCCH coincides with the system ID registered in the memory 1008 in the FSU when the FSU searches for the LCCH of the wireless base station, the control portion 1005 controls the channel codec portion 1004 to grasp the wireless base station, after the FSU performs data exchange, through wireless line, of the position registration sequence defined in RCR-STD-28, under the control by the control portion 1005 and the channel codec portion 1004, the FSU gets in a standby state in the same manner as the mobile station of a general PHS. By the position registration, the position information of the FSU is sent from the base station to the telephone central office, so that the FSU can receive signals.
The transmitting operation of the FSU will be described below. FIG. 13 is a schematic diagram of a telephone-FSU-base station transmission sequence based on a batch transmission sequence diagram defined in RCR STD-28. When a telephone C connected to the FSU is hooked off and sends out a specific dial after the position registration, the control portion 1005 makes the telephone off-hook/on-hook detecting circuit 1007d of the telephone line interface portion 1007 of FIG. 10 detect an off-hook signal from the telephone C. Upon detection of the off-hook signal, the control portion 1005 makes the tone generating circuit 1007e of the telephone line interface portion 1007 output a dial tone to the telephone C.
Hearing the dial tone, the user pushes down the dial of the telephone. In the FSU, the control portion 1005 controls the telephone dial detecting circuit 1007e of the telephone line interface portion 1007 to detect the dial from the telephone C. The control portion 1005 sets a predetermined waiting time in a dial input waiting timer. When the timer expires, data exchange in the batch transmission sequence defined in RCR STD-28 is performed on wireless line by means of the control portion 1005 and the channel codec portion 1004. When communication connection succeeds, the control portion 1005 operates the voice codec portion 1007a of the telephone line interface portion 1007, so that the user can hear, through the telephone, a ringback tone (hereinafter referred to as RBT) which is a sound outputted from the telephone central office to call a remote-side telephone through the base station and the FSU. The user waits for the response of the remote-side telephone so that the user can make speech with the remote-side telephone through the telephone C when the remote-side telephone makes a response.
FIG. 14 is a schematic diagram of a telephone-FSU-base station reception and reception response sequence based on a reception sequence diagram defined in RCR STD-28. When there is a reception from the remote-side telephone, first, communication based on the reception sequence defined in RCR STD-28 is performed between the wireless base station E and the FSU by means of the control portion 1005 and channel codec portion 1004 in the FSU. When the reception sequence succeeds, the FSU makes the control portion 1005 control the reception signal generating circuit 1007c of the telephone line interface portion 1007 to send out a reception signal to the telephone C, so that a ringer sound is generated from the telephone C to inform the telephone user of the reception. When the user hooks off the telephone in the reception state, the control portion 1005 of the FSU controls the telephone off-hook/on-hook detecting circuit 1007d of the telephone line interface portion 1007 to detect the off-hook signal from the telephone C. The control portion 1005 controls the channel codec portion 1004 and the wireless circuit 1001 to transmit a response message to the wireless base station E by wireless. When the FSU receives a response confirmation message from the wireless base station E, the reception response is established so that the user can make a speech with the user of the remote-side telephone through the telephone C.
In the telephone line interface portion in the aforementioned conventional WLL fixed subscriber unit, the telephone off-hook/on-hook detecting circuit and the telephone dial detecting circuit are provided separately from each other. Accordingly, if the control portion is achieved on the consideration that all standards of pulse dials in telephones used in various countries in the world are satisfied, that is, if the control portion is configured so that a DTMF (dual tone multi-frequency) type telephone dial is detected by the telephone dial detecting circuit and that a pulse dial type telephone dial is detected by the off-hook/on-hook detecting circuit, there arises a problem that the telephone pulse dial signal may be detected so as to be mistaken for a hooking signal.